Sorry, but a DTED is a simple matrix terrain model, not a vector TIN.
If you wanna know more about a transformation DEM-to-VECTOR, read this (in italian).
Anyway, you can convert a classic Dem into a Dted by means of the free Microdem.
About sectioning a Dem, never tried it, but I'd before convert it to a vector mesh, then slice it.
Buongiorno,
devo ammettere che a suo tempo mi fu molto utile la risposta.
Grazie
in ritardo 😉